Acute Lung Injury (ALI) leads to the Acute Respiratory Distress Syndrome (ARDS), which is deadly to children and adults. In ALI, lung microvascular hyperpermeability causes pulmonary edema, leading to oxygenation failure characteristic of ARDS. Currently, there is no specific therapy for ARDS and treatment is supportive. Thus, there is a need for more understanding of ALI mechanisms in order to develop potential therapeutics. Dr. Rebecca Hough?s research is aimed at understanding how, in ALI, an injurious signal is communicated from alveoli to microvessels, resulting in microvascular hyperpermeability and pulmonary edema. Dr. Hough has found that mitochondria in microvessels can sense injury through oxidative activation of the proton channel uncoupling protein 2 (UCP2). UCP2 activation is necessary for microvascular hyperpermeability and pulmonary edema. This proposal uses microscopy of live mouse lungs. Using this specialized technique, Dr. Hough can view individual alveoli in real-time and observe the immediate effects of lung injury on mitochondria in alveoli and microvessels. In this proposal, Dr. Hough will expand her research to ask four questions: (1) Does a prolonged inflammatory injury, such as pneumonia or high tidal volume mechanical ventilation, cause barrier failure in a UCP2-dependent manner?; (2) Does UCP2 activation in endothelium underlie lung injury from non-pulmonary causes, such as sepsis?; (3) Is there a directionality of oxidative signaling exclusively from alveolus to capillary, or can the signaling be bidirectional?; and (4) Does UCP2 underlie barrier failure and severe hypoxemia in the young? This proposal details a 5-year research plan designed to give Dr. Hough a foundation as an independent investigator. Dr. Hough will conduct a novel mechanistic research project under the mentorship of outstanding lung researcher Dr. Jahar Bhattacharya, and the co-mentorship of renowned development lung biologist Dr. Wellington Cardoso. She will (1) develop her expertise in real-time fluorescence imaging of live mouse lungs and human lungs from deceased donors, as well as animal models of lung injury, (2) build a network of collaborators via participation at national meetings, and (3) prepare and submit an independent federal research grant within 5 years. As a pediatric intensivist, Dr. Hough aims to take what she has learned about UCP2 and its importance in barrier failure associated with ARDS and apply this knowledge to infants and children.